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參數資料
| 型號： | AD7864AS-2 |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | ADC |
| 英文描述： | 4-Channel, Simultaneous Sampling, High Speed, 12-Bit ADC |
| 中文描述： | 4-CH 12-BIT SUCCESSIVE APPROXIMATION ADC, PARALLEL ACCESS, PQFP44 |
| 封裝： | PLASTIC, MO-112-AA, MQFP-44 |
| 文件頁數： | 15/19頁 |
| 文件大小： | 214K |
| 代理商： | AD7864AS-2 |
AD7864
–15–
REV. A
ADC CODE
1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064
9000
8000
0
4000
3000
2000
1000
6000
5000
7000
Figure 14. Histogram of 8192 Conversions of a DC Input
The output spectrum from the ADC is evaluated by applying a
sine wave signal of very low distortion to the analog input. A
Fast Fourier Transform (FFT) plot is generated from which the
SNR data can be obtained. Figure 15 shows a typical 4096 point
FFT plot of the AD7864 with an input signal of 99.9 kHz and a
sampling frequency of 500 kHz. The SNR obtained from this
graph is 72.6 dB. It should be noted that the harmonics are
taken into account when calculating the SNR.
FREQUENCY – Hz
0
50000
100000
150000
200000
250000
0
–10
–90
–50
–60
–70
–80
–30
–40
–20
–110
–100
d
AD7864-1 @ +25
8
C
5V SUPPLY
SAMPLING AT 499712Hz
INPUT FREQUENCY OF 99857Hz
8192 SAMPLES TAKEN
Figure 15. FFT Plot
Effective Number of Bits
The formula given in Equation 1 relates the SNR to the number
of bits. Rewriting the formula, as in Equation 2, it is possible to
get a measure of performance expressed in effective number of
bits (N).
N
=
SNR
–1.76
6.02
The effective number of bits for a device can be calculated di-
rectly from its measured SNR. Figure 16 shows a typical plot
of effective number of bits versus frequency for an AD7864-2.
(2)
FREQUENCY – kHz
12
4
E
11
8
7
6
5
10
9
0
3000
500
1000
1500
2000
2500
–40
8
C
+25
8
C
+105
8
C
Figure 16.Effective Numbers of Bits vs. Frequency
Intermodulation Distortion
With inputs consisting of sine waves at two frequencies, fa and
fb, any active device with nonlinearities will create distortion
products at sum and difference frequencies of mfa
±
nfb where
m, n = 0, 1, 2, 3 . . ., etc. Intermodulation terms are those for
which neither m or n are equal to zero. For example, the second
order terms include (fa + fb) and (fa – fb) while the third order
terms include (2fa + fb), (2fa – fb), (fa + 2fb) and (fa – 2fb).
Using the CCIF standard where two input frequencies near the
top end of the input bandwidth are used, the second and third
order terms are of different significance. The second order terms
are usually distanced in frequency from the original sine waves
while the third order terms are usually at a frequency close to
the input frequencies. As a result, the second and third order
terms are specified separately. The calculation of the intermodu-
lation distortion is as per the THD specification where it is the
ratio of the rms sum of the individual distortion products to the
rms amplitude of the fundamental expressed in dBs. In this
case, the input consists of two, equal amplitude, low distortion
sine waves. Figure 17 shows a typical IMD plot for the AD7864.
FREQUENCY – Hz
0
10000
20000
30000
40000
50000
0
–10
–90
–50
–60
–70
–80
–30
–40
–20
–100
d
60000
AD7864-1 @ +25
8
C
5V SUPPLY
SAMPLING AT 131072Hz
INPUT FREQUENCIES OF
48928Hz AND 50016Hz
4096 SAMPLES TAKEN
Figure 17. IMD Plot
相關PDF資料 |
PDF描述 |
|---|---|
| AD7864AS-3 | 4-Channel, Simultaneous Sampling, High Speed, 12-Bit ADC |
| AD7864AS | IC-SM-12-BIT ADC |
| AD7865YS-1 | Four-Channel, Simultaneous Sampling, Fast, 14-Bit ADC |
| AD7865YS-2 | Four-Channel, Simultaneous Sampling, Fast, 14-Bit ADC |
| AD7865YS-3 | Four-Channel, Simultaneous Sampling, Fast, 14-Bit ADC |
相關代理商/技術參數 |
參數描述 |
|---|---|
| AD7864AS-2REEL | 制造商:Analog Devices 功能描述:ADC Single SAR 520ksps 12-bit Parallel 44-Pin MQFP T/R |
| AD7864AS-2Z | 制造商:Analog Devices 功能描述:ADC 12BIT 4CH 500KSPS 44MQ 制造商:Analog Devices 功能描述:ADC, 12BIT, 4CH, 500KSPS, 44MQFP; Resolution (Bits):12bit; Sampling Rate:520kSPS; Supply Voltage Type:Single; Supply Voltage Min:4.75V; Supply Voltage Max:5.25V; Supply Current:24mA; Digital IC Case Style:MQFP; No. of Pins:44; Input ;RoHS Compliant: Yes |
| AD7864AS-3 | 制造商:Analog Devices 功能描述:ADC Single SAR 520ksps 12-bit Parallel 44-Pin MQFP 制造商:Analog Devices 功能描述:IC 12-BIT ADC |
| AD7864AS-3REEL | 制造商:Analog Devices 功能描述:ADC Single SAR 520ksps 12-bit Parallel 44-Pin MQFP T/R |
| AD7864AS-3Z | 制造商:Analog Devices 功能描述:ADC 12BIT 4CH 500KSPS 44MQ 制造商:Analog Devices 功能描述:ADC, 12BIT, 4CH, 500KSPS, 44MQFP; Resolution (Bits):12bit; Sampling Rate:520kSPS; Supply Voltage Type:Single; Supply Voltage Min:4.75V; Supply Voltage Max:5.25V; Supply Current:24mA; Digital IC Case Style:MQFP; No. of Pins:44; Input ;RoHS Compliant: Yes |
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